Spray Foam Insulation R Values

R values are additive so you can multiple the number of inches of insulation thickness times the r value to arrive at a total insulation value.

Spray foam insulation r values.

Open cell spray foam insulation is air impermeable and is applied with a minimum of 3 5 on average and can be used for attics interior floors walls and soundproofing. All these have r values ranging from r 3 2 to r 3 8 per inch. Rigid foam boards trap air or another gas to resist conductive heat flow. Bulky materials resist conductive and to a lesser degree convective heat flow in a building cavity.

It performs much better than any form of batt for stopping air flow but it is not as complete of an air seal as closed cell spray foam. The r value for open cell is typically around 3 7 at 1 thick and varies by manufacture. The r value of closed cell foam is r 6 5 7 per inch. For example if you have a type of insulation that has an r value of r 5 per inch of thickness you will need a depth of 6 inches of this insulation installed in your attic to reach r 30 if you live in zones 2 or 3.

Contractors often use it to insulate under slabs ceilings walls and roofs. These r values are a sum meaning this should be the total r value once you add up the entire depth of insulation. Open cell spray foam typically has an r value of 3 5 per inch and it should be noted that open cell does not form a tight air seal. Spray foam the truth about r values r value does not measure heat movement carried in the air.

Insulation r value measures how well a particular insulation resists heat flow. The r value of fiberglass insulation is approximately 2 2 per inch so much thicker fiberglass insulation is required to achieve the same r value of 38. Closed cell spray foam has a far better r value per inch than other less effective insulations like cellulose fiberglass or even open cell foam. When the time comes to assess the type of insulation your home needs r value is a common term you will hear.